Research on deformation behavior, microstructure evolution and phase transformation of ultra-light LA93-1(La/Ce) alloy

Abstract

Isothermal compression tests were conducted out on the Mg–9Li–3Al-1(La/Ce) (wt.%) alloy under different deformation parameter through a Gleeble-3500 thermal-mechanical simulator. The flow curves at high strain rates exhibit a ''serrated flow”, which is a dynamic strain aging behavior. R = 0.9253 and AARE = 7.64% quantified the accuracy of the constitutive equations, indicating that this equation has reliable predictive ability. The thermal processing maps indicated that the safe processing region is T = 537–623 K, ε˙ = 0.041–0.001 s−1. This alloy has excellent formability. When deformation is at T = 473 K, ε˙ = 1 s−1, there are more deformed grains in two phases, and broken β-Li grains distributed in chains along the RD. In addition, some α-Mg phases precipitated from the β-Li phase, distributed along the β-Li grain boundaries, and they were dominated by recrystallized grains with low dislocation density. High-density dislocation regions located both at the grain boundaries and inside the grains. When deformation is at T = 473 K, ε˙ = 0.01 s−1, all the deformed grains in two phases decreased with decreasing strain rate, and they transformed more into substructures. The high-density dislocation regions inside the grains gradually disappear. Additionally, the size of precipitated α-Mg phase increased slightly, which is still predominantly located at the grain boundaries. When deformation is at T = 623 K, ε˙ = 0.01 s−1, the degree of recrystallization increases significantly with increasing temperature. The high-density dislocation regions almost disappeared. Interestingly, large amounts of α-Mg grains precipitated inside the β-Li grains.

Keywords

• Microstructure evolution
• Strain-induced transformation
• Thermal processing map
• Deformation behavior